Metallic containers offer distributors and consumers many benefits. The metallic body of a container provides optimal protection properties for products. For example, the metallic body prevents CO2 migration and UV radiation which may damage personal care, pharmaceutical, and food products and other UV-sensitive formulations, negatively influencing the effectiveness of ingredients, as well as the fragrance, flavor, appearance, or color of the product. Metallic containers also offer an impermeable barrier to light, water vapor, oils and fats, oxygen, and micro-organisms and keep the contents of the container fresh and protected from external influences, thereby guaranteeing a long shelf-life.
Additionally, the increased durability of metallic containers compared to glass and plastic containers reduces the number of containers damaged during processing and shipping, resulting in further savings. Metallic containers are also lighter than glass containers resulting in energy savings during shipment. Further, metallic containers, such as aerosol containers, have significant durability and are difficult to deform or burst and thus are highly valuable for holding products under pressure. Finally, recycling metallic containers is easier than recycling glass and plastic containers because labels and other indicia are printed directly onto the metallic body while glass and plastic containers typically have labels that must be separated during the recycling process.
Methods of manufacturing metallic aerosol containers are known in the container industry and may include a process where a metallic cup is formed in a draw and wall ironing (DWI) process. The manufacture of the metallic cup in a DWI process requires a number of separate processing steps. The manufacture of the metallic container body typically starts by forming a cup from a metallic stock material which is typically shipped and stored in large coils. The coil of metallic material is fed into a blank-and-draw press which cuts a generally circular blank of a predetermined diameter from the coil and draws the blank into a smaller diameter cylinder one or more times to produce a formed cup. As appreciated by one skilled in the art, numerous varieties of blank, draw, and redraw steps may be performed to initially form a cylindrical shaped cup.
Alternatively, the metallic container body may be formed at least partially by an impact extrusion process. Impact extrusion is a process utilized to make metallic containers and other articles with unique shapes from metallic slugs. The slugs are typically made from a softened metal slug comprised of steel, magnesium, copper, aluminum, tin, and lead and other alloys. The metallic container body is formed inside a confining die from a cold slug which is contacted by a punch. The force from the punch deforms the metal slug around an outer diameter of the punch and the inner diameter of the confining die to make a formed cup.
The formed cup from the blank-and-draw press or the impact extrusion press is transferred to a second press where it is redrawn and ironed. An open end of the formed cup is then trimmed to a predetermined height forming a trimmed metallic container body. A shoulder and a neck portion with a reduced diameter are then formed in the closed end portion of the metallic container body in a number of successive operations.
Prior art methods of forming a shoulder and a neck portion on a metallic container body are described in U.S. Pat. No. 2,337,182 to Calleson et al. (“Calleson”) and U.S. Pat. No. 3,726,244 to Arangelovich et al. (“Arangelovich”) which are each incorporated herein by reference in their entireties. Calleson and Arangelovich utilize tools and methods for forming a shoulder and neck on the closed end of a container that are slow and utilize tools with linear, flat faces. Both patents also teach the use of a punch that contacts an interior portion of the closed end to form an opening therein before the formation of the shoulder and the neck are completed. Further, both Calleson and Arangelovich form a shoulder that is straight and does not provide an aesthetically pleasing, rounded shoulder.
Other methods of forming a shoulder and neck portion on a closed end of a metallic container body are described in U.S. Pat. Nos. 6,499,329 and 6,857,304 which are assigned to Daiwa Can Company and which are each incorporated herein by reference in their entireties. The shoulder of the metallic container is formed in a sequential process with forming steps sequentially using tools with linear, flat end portions. The shoulder is extended and smoothed between a pair of forming tools after the final neck diameter is formed to remove the wrinkling of the shoulder portion, while extending the overall length of the neck portion. The presses used in the methods described in these patents are generally difficult to service and calibrate due to the inaccessibility of the dozens of tooling stations and other components and excessive material wrinkling may occur during shoulder forming.
Accordingly, there is an unmet need for a high speed method and apparatus of forming a contoured shoulder and neck portion on a metallic container such as a two-piece aerosol container with an improved appearance, efficiency, and cost.